1. Field of the Invention
The invention relates to the front pulley of a treadmill and, more particularly, to a new invention that keeps on a parallel with the rear pulley automatically and eliminates the instant idling phenomenon between the front pulley and the running belt.
2. Description of the Prior Art
As shown in FIG. 1, a treadmill 10 is caterpillar-type indoor exercising equipment which comprises mainly a frame 11 with a front and a rear pulleys 12 and 13 integrated at its front and rear ends. A running belt 20 encircles the front and rear pulleys 12 and 13. As a user runs on the running belt 20, the running belt 20 circulates around the front and rear pulleys 12 and 13 continuously without translocation. In order to make the running belt 20 continuously circulates around the front and rear pulleys 12 and 13 smoothly, the pulleys 12 and 13 must always be parallel to each other and the running belt 20 must be taut to avoid the instant idling phenomenon.
Referring to FIG. 2, an assembling diagram of a prior front pulley of a treadmill, positioning plates 21 having holes are disposed at both sides of each of the front and rear ends to locate the front and rear pulleys 12 and 13 in the holes of their corresponding positioning plate 21 by their own shafts 14. A flywheel 16 integrated on one side of the front pulley 12 connects to the shaft 19 of a motor 18 by a belt 17. Therefore, when the motor 18 operates, the front pulley 12 is rotated, thereby driving the running belt 20 to circulale around the front and rear pulleys 12 and 13 continuously.
A screw hole is disposed on the shaft 14 at one side of the front pulley 12 to keep the front pulley 12 and the rear pulleys 13 in parallel, and an adjusting screw 23 is screwed on the outside of the positioning plate 21 located there. Therefore, the position and angle of the front pulley 12 can be adjusted by the action of the adjusting screw 23.
However, since the front pulley 12 must be adjusted and corrected to be parallel to the rear pulley 13 during assembling it takes much time to assemble and repeated testing is required. In addition processing of the front pulley 12 is complex, thus increasing the fabricating cost.
Besides, locations of the front and rear pulleys 12 and 13 and tile running belt 20 are fixed after assembling and the running belt 20 is driven to circulate by the front pulley 12. When a downward force is applied to the running belt 20, the running belt 20 is forced and is instantly tightened. However, the front pulley 12 keeps on swiveling as being driven by the motor 18. The contact point between the running belt 20 and the rear pulley 13 becomes tighter while the contact point between the running belt 20 and the front pulley 12 gets looser, and an idling phenomenon may occur between the running belt 20 and the front pulley 12. To put it briefly, the running belt 20 may be stuck instantly. Although the stuck phenomenon takes only a very short time, the user may become off balance, just like the heel of a running is stamped during running, thus serious injury may take place.